The LDL-Receptor Family. In: Spik G, Legrand D, Mazurier J, Pierce A, Perraudin J, editors. Advances in Lactoferrin Research. Boston: Springer US; 1998. pp. 107-11. [DOI: 10.1007/978-1-4757-9068-9_13]

To Boost or to Reset: The Role of Lactoferrin in Energy Metabolism

Many pathological conditions, including obesity, diabetes, hypertension, heart disease, and cancer, are associated with abnormal metabolic states. The progressive loss of metabolic control is commonly characterized by insulin resistance, atherogenic dyslipidemia, inflammation, central obesity, and hypertension, a cluster of metabolic dysregulations usually referred to as the "metabolic syndrome". Recently, nutraceuticals have gained attention for the generalized perception that natural substances may be synonymous with health and balance, thus becoming favorable candidates for the adjuvant treatment of metabolic dysregulations. Among nutraceutical proteins, lactoferrin (Lf), an iron-binding glycoprotein of the innate immune system, has been widely recognized for its multifaceted activities and high tolerance. As this review shows, Lf can exert a dual role in human metabolism, either boosting or resetting it under physiological and pathological conditions, respectively. Lf consumption is safe and is associated with several benefits for human health, including the promotion of oral and gastrointestinal homeostasis, control of glucose and lipid metabolism, reduction of systemic inflammation, and regulation of iron absorption and balance. Overall, Lf can be recommended as a promising natural, completely non-toxic adjuvant for application as a long-term prophylaxis in the therapy for metabolic disorders, such as insulin resistance/type II diabetes and the metabolic syndrome.

Deciphering the Interactome of Neisseria meningitidis With Human Brain Microvascular Endothelial Cells

Neisseria meningitidis is able to translocate the blood-brain barrier and cause meningitis. Bacterial translocation is a crucial step in the onset of neuroinvasion that involves interactions between pathogen surface proteins and host cells receptors. In this study, we applied a systematic workflow to recover and identify proteins of N. meningitidis that may interact with human brain microvascular endothelial cells (hBMECs). Biotinylated proteome of N. meningitidis was incubated with hBMECs, interacting proteins were recovered by affinity purification and identified by SWATH-MS. Interactome of N. meningitidis comprised of 41 potentially surface exposed proteins. These were assigned into groups based on their probability to interact with hBMECs: high priority candidates (21 outer membrane proteins), medium priority candidates (14 inner membrane proteins) and low priority candidates (six secretory proteins). Ontology analysis provided information for 17 out of 41 surface proteins. Based on the series of bioinformatic analyses and literature review, five surface proteins (adhesin MafA1, major outer membrane protein P.IB, putative adhesin/invasion, putative lipoprotein and membrane lipoprotein) were selected and their recombinant forms were produced for experimental validation of interaction with hBMECs by ELISA and immunocytochemistry. All candidates showed interaction with hBMECs. In this study, we present a high-throughput approach to generate a dataset of plausible meningococcal ligands followed by systematic bioinformatic pipeline to categorize the proteins for experimental validation.

Bovine Lactoferrin Inhibits Dengue Virus Infectivity by Interacting with Heparan Sulfate, Low-Density Lipoprotein Receptor, and DC-SIGN

Bovine lactoferrin (bLF) presents in milk and has been shown to inhibit several viral infections. Effective drugs are unavailable for the treatment of dengue virus (DENV) infection. In this study, we evaluated the antiviral effect of bLF against DENV infection in vivo and in vitro. Bovine LF significantly inhibited the infection of the four serotypes of DENV in Vero cells. In the time-of-drug addition test, DENV-2 infection was remarkably inhibited when bLF was added during or prior to the occurrence of virus attachment. We also revealed that bovine LF blocks binding between DENV-2 and the cellular membrane by interacting with heparan sulfate (HS), dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN), and low-density lipoprotein receptors (LDLR). In addition, bLF inhibits DENV-2 infection and decreases morbidity in a suckling mouse challenge model. This study supports the finding that bLF may inhibit DENV infection by binding to the potential DENV receptors.

Bovine lactoferrin inhibits Japanese encephalitis virus by binding to heparan sulfate and receptor for low density lipoprotein

Lactoferrin is a natural anti-microbial protein which affects Japanese encephalitis virus (JEV) activity. Binding of lactoferrin to cell surface expressed heparan sulfate (HS), one possible receptor for JEV, has been postulated to be the possible mechanism of anti-JEV antiviral activity. In this study, we evaluate the effects of bovine lactoferrin (bLF) against JEV infection in vitro, using both wild-type (WT) and laboratory-adapted strains. bLF inhibited the infectivity of all the JEV strains tested. In particular the infectivity of the HS-adapted JEV strains was strongly reduced, whereas the non HS-adapted JEV strains were inhibited to lesser extent. Using both HS-adapted CJN-S1 and non HS-adapted CJN-L1 viruses, the results showed that bLF inhibited the early events essential to initiate JEV infection, which includes blocking virus attachment to cellular membranes and reducing viral penetration. This anti-JEV activity was the highest using HS-adapted CJN-S1 strain on HS-expressed CHO-K1 cells. Also, binding of bLF to heparin-sepharose blocked JEV binding; and soluble HS attenuated the anti-JEV activity of bLF. The results support the premise that the interaction of bLF with cell surface expressed glycosaminoglycans, in particular the highly sulfated HS, plays an essential role in the antiviral activity of bLF. However, bLF was functional in inhibiting CJN-S1 entry into HS-deficient CHO-pgsA745 cells, and bLF-treated CHO-K1 and -pgsA745 cells also prevented non HS-adapted CJN-L1 virus entry, indicating that a non-HS pathway may be involved in bLF inhibition of JEV entry. The low-density lipoprotein receptor (LDLR), possibly involved in the entry of several RNA viruses, also binds to bLF. We found that both rLDLR and anti-LDLR antibodies reduced the effectiveness of bLF inhibition of JEV infection. This finding provided evidence to suggest that cell surface-expressed LDLR may play a role in JEV infection, especially for non HS-adapted strains.

Iron transport systems in Neisseria meningitidis

Acquisition of iron and iron complexes has long been recognized as a major determinant in the pathogenesis of Neisseria meningitidis. In this review, high-affinity iron uptake systems, which allow meningococci to utilize the human host proteins transferrin, lactoferrin, hemoglobin, and haptoglobin-hemoglobin as sources of essential iron, are described. Classic features of bacterial iron transport systems, such as regulation by the iron-responsive repressor Fur and TonB-dependent transport activity, are discussed, as well as more specific features of meningococcal iron transport. Our current understanding of how N. meningitidis acquires iron from the human host and the vaccine potentials of various components of these iron transport systems are also reviewed.